Transmission of acknowledgement signals from a user equipment for orthogonal reception at multiple points

ABSTRACT

Methods and user equipment (UE) apparatuses are provided to transmit an acknowledgement/negative acknowledgement (ack/nack) signal. A method includes receiving configuration information through higher layer signaling; determining a first resource or a second resource based on the received configuration information; transmitting the ack/nack signal using a first sequence on the first resource, if the first resource is determined; and transmitting the ack/nack signal using a second sequence on the second resource, if the second resource is determined.

PRIORITY

This application is a Continuation of U.S. Ser. No. 14/693,577, whichwas filed in the United States Patent and Trademark Office (USPTO) onApr. 22, 2015, which is a Continuation of U.S. Ser. No. 13/630,802,which was filed in the USPTO on Sep. 28, 2012, and claims priority under35 U.S.C. §119(e) to United States Provisional Applications filed in theUSPTO on Sep. 30, 2011 and Jun. 7, 2012, and assigned Ser. Nos.61/541,441 and 61/656,729, respectively, the entire content of each ofwhich is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to wireless communicationsystems and more specifically, to transmission power control of soundingreference signals.

2. Description of the Art

A communication system includes a DownLink (DL) that conveys signalsfrom at least one Transmission Point (TP) to User Equipments (UEs), andan UpLink (UL) that conveys signals from UEs to at least one ReceptionPoint (RP). A UE, also referred to as a fixed or mobile terminal or amobile station, includes a wireless device, a cellular phone, a personalcomputer device, and the like. A TP or an RP is generally a fixedstation and is also referred to as a Base Transceiver System (BTS), aNodeB, an access point, and the like.

A communication system also supports several signal types oftransmissions including data signals conveying information content,control signals enabling proper processing of data signals, andReference Signals (RS), also known as pilots, enabling coherentdemodulation of data or control signals or providing Channel StateInformation (CSI) corresponding to an estimate of a channel mediumexperienced by their transmissions.

DL data information is conveyed through a Physical DL Shared CHannel(PDSCH). DL Control Information (DCI) includes Scheduling Assignments(SAs) for Physical UL Shared CHannel (PUSCH) transmissions from UEs (ULSAs) or for PDSCH receptions by UEs (DL SAs). The SAs are conveyedthrough DCI formats transmitted in respective Physical DL ControlCHannels (PDCCHs). In addition to SAs, PDCCHs may convey DCI that iscommon to all UEs or to a group of UEs. DCI also includes ACKnowledgment(ACK) information associated with a Hybrid Automatic Repeat reQuest(HARQ) ACK (HARQ-ACK) process transmitted to UEs from at least one TPthrough Physical HARQ-ACK Indicator CHannels (PHICHs) in response torespective receptions at RPs of data Transport Blocks (TBs) transmittedfrom the UEs.

UL data information is conveyed through a Physical UL Shared CHannel(PUSCH). UL Control Information (UCI) is conveyed through a Physical ULControl CHannel (PUCCH), unless a UE also transmits a PUSCH, in whichcase the UE may convey at least some UCI in the PUSCH. UCI includesHARQ-ACK information and is transmitted in response to a reception by aUE of data TBs. HARQ-ACK signaling is periodic or dynamic, if arespective reception of data TBs by a UE is semi-persistently(periodically) scheduled without a respective PDCCH or dynamicallyscheduled by a PDCCH. Other periodically transmitted UCI signalingincludes DL CSI informing a NodeB of a channel medium experienced by asignal transmission to a UE and Scheduling Request (SR) informing aNodeB that a respective UE has data to transmit. A UL RS is used fordemodulation of data or control signals, in which case the UL RS isreferred to as DeModulation RS (DMRS), or to sound a UL channel mediumand provide NodeBs with UL CSI, in which case it is referred to as aSounding RS (SRS).

Typically, PDCCHs are a major part of a DL overhead. One method forreducing this overhead is to scale its size according to the resourcesrequired to transmit the PDCCHs and PHICHs in a DL Transmission TimeInterval (TTI). Assuming Orthogonal Frequency Division Multiple Access(OFDMA) as the DL transmission method, a Control Format Indicator (CFI)parameter is transmitted through a Physical Control Format IndicatorCHannel (PCFICH) to indicate a number of OFDM symbols allocated to a DLcontrol region during a DL TTI.

FIG. 1 is a diagram illustrating a conventional structure for a DLcontrol region in a DL TTI.

Referring to FIG. 1, a DL TTI includes one subframe having M symbols anda DL control region occupies a first N subframe symbols 110. Theremaining M-N subframe symbols are primarily used to transmit PDSCHs120. A PCFICH 130 is transmitted in some sub-carriers, also referred toas Resource Elements (REs) of the first symbol and conveys 2 bitsindicating a PDCCH size of M=1, or M=2, or M=3 symbols. A PHICH 140 isalso transmitted in some REs of the first symbol. Moreover, some symbolsalso contain RS REs, 150 and 160, that are common to all UEs for each ofthe TP antenna ports which in FIG. 1 are assumed to be two ports. Themain purposes of UE-Common RS (CRS) are to enable a UE to obtain achannel estimate for its DL channel medium and to perform othermeasurements and functions. The remaining REs in the DL control regionare used to transmit PDCCHs.

PDCCHs conveying SAs are not transmitted at predetermined locations in aDL control region and, as a consequence, each UE needs to performmultiple decoding operations to determine whether it has an SA in a DLsubframe. To assist a UE with the multiple decoding operations, REscarrying a PDCCH are grouped into Control Channel Elements (CCEs) in thelogical domain. For a given number of DCI format bits, a number of PDCCHCCEs depends on a channel coding rate, assuming Quadrature Phase ShiftKeying (QPSK) as the modulation scheme. For UEs experiencing low or highDL Signal-to-Interference and Noise Ratio (SINR), TPs may respectivelyuse a low or high channel coding rate for a PDCCH transmission in orderto achieve a desired BLock Error Rate (BLER). Therefore, a PDCCHtransmission to a UE experiencing low DL SINR may require more CCEs thana PDCCH transmission to a UE experiencing high DL SINR (different powerboosting of REs of a CCE may also apply). Typical CCE aggregation levelsfor a PDCCH are, for example, of 1, 2, 4, and 8 CCEs.

For a PDCCH decoding process a UE determines a search space forcandidate PDCCHs according to a common set of CCEs for all UEs (CommonSearch Space or CSS) and according to a UE-dedicated set of CCEs(UE-Dedicated Search Space or UE-DSS). The CSS may consist of the firstN_(CCE) ^(UE-CSS) CCEs in the logical domain. The UE-DSS is determinedaccording to a pseudo-random function having as inputs UE-commonparameters, such as a subframe number or a total number of CCEs in asubframe, and UE-specific parameters such as a Radio Network TemporaryIdentifier (RNTI). For example, for CCE aggregation levels Lε{1,2,4,8},the CCEs for PDCCH candidate m are given by L·{(Y_(k)+m) mod└N_(CCE,k)/L┘}+i where N_(CCE,k) is a total number of CCEs in subframek, i=0, . . . , L−1, m=0, . . . , M^((L))−1, M^((L)) is a number ofPDCCH candidates to monitor in a search space, and └ ┘ is the “floor”function rounding a number to its immediately smaller integer. Exemplaryvalues of M^((L)) for Lε{1,2,4,8} are, respectively, {0, 0, 4, 2} in theUE-CSS, and {6, 6, 2, 2} in the UE-DSS. For the CSS, Y_(k)=0. For theUE-DSS, Y_(k)=(A·Y_(k-1))mod D where Y⁻¹=RNTI≠0, A=39827 and D=65537.

PDCCHs conveying information to multiple UEs, such as a PDCCH conveyingTransmission Power Control (TPC) commands for UEs for adjustingrespective PUSCH or PUCCH transmission powers, are transmitted in theCSS. If enough CCEs remain in the CSS after transmitting PDCCHsconveying DCI to multiple UEs in a subframe, the CSS is also used totransmit PDCCHs providing SAs with specific DCI formats. The UE-DSS isexclusively used to transmit PDCCHs providing SAs. For example, the CSSmay consist of 16 CCEs and support 2 PDCCHs with L=8 CCEs, or 4 PDCCHswith L=4 CCEs, or 1 PDCCH with L=8 CCEs and 2 PDCCHs with L=4 CCEs. TheCCEs for the CSS are placed first in the logical domain (prior to aninterleaving of CCEs).

FIG. 2 is a diagram illustrating a conventional PDCCH transmissionprocess.

Referring to FIG. 2, after channel coding and rate matching, encodedbits of DCI formats are mapped to CCEs in the logical domain. The first4 CCEs (L=4), CCE1 201, CCE2 202, CCE3 203, and CCE4 204 are used totransmit PDCCH to UE1. The next 2 CCEs (L=2), CCE5 211 and CCE6 212, areused to transmit PDCCH to UE2. The next 2 CCEs=2), CCE7 221 and CCE8222, are used to transmit PDCCH to UE3. Finally, the last CCE (L=1),CCE9 231, is used to transmit PDCCH to UE4. The DCI format bits of aPDCCH is scrambled 240 with a binary scrambling code and aresubsequently modulated 250. Each CCE is further divided into ResourceElement Groups (REGs). For example, a CCE including 36 REs is dividedinto 9 REGs, each including 4 REs. Interleaving 260 is applied amongREGs (blocks of 4 QPSK symbols). For example, a block interleaver isused with interleaving performed on symbol-quadruplets (4 QPSK symbolscorresponding to 4 REs of a REG) instead of on individual bits. AfterREG interleaving, a resulting series of QPSK symbols is shifted by Jsymbols 270, and finally each QPSK symbol is mapped to an RE 280 in theDL control region of a subframe. Therefore, in addition to RS from TPantenna ports, 291 and 292, and other control channels such as a PCFICHor a PHICH 293, REs in a DL control contain QPSK symbols correspondingto DCI formats for UE1 294, UE2 295, UE3 296, and UE4 297.

After the reception of a PDSCH, a UE transmits HARQ-ACK information in aPUCCH to indicate the correct (ACK) or incorrect (NACK) reception ofdata TBs in a PDSCH.

FIG. 3 is a diagram illustrating a conventional structure for HARQ-ACKsignal transmission in a PUCCH.

Referring to FIG. 3, HARQ-ACK signals, and RS enabling coherentdemodulation of HARQ-ACK signals, are transmitted in one slot 310 of aPUCCH subframe including 2 slots. HARQ-ACK information bits 320 modulate330 a Zadoff-Chu (ZC) sequence 340, for example using BPSK or QPSK,which is then transmitted after performing an Inverse Fast FourierTransform (IFFT) operation. Each RS 350 is transmitted through anunmodulated ZC sequence.

For a UL system BandWidth (BW) including N_(RB) ^(max,UL) ResourceBlocks (RBs), where each RB includes N_(sc) ^(RB)=12 REs, a ZC sequencer_(u,v) ^((α))(n) is defined by a Cyclic Shift (CS) α of a base ZCsequence r _(u,v) (n) according to r_(u,v) ^((α))(n)=e^(jαn) r_(u,v)(n), 0≦n<M_(sc) ^(RS), where M_(sc) ^(RS)=mN_(sc) ^(RB) is alength of a ZC sequence, 1≦m≦N_(RB) ^(max,UL), and r _(u,v)(n)=x_(q) (nmod N_(ZC) ^(RS)) where the q^(th) root ZC sequence is defined by

${{x_{q}(m)} = {\exp\left( \frac{{- j}\;\pi\;{{qm}\left( {m + 1} \right)}}{N_{ZC}^{RS}} \right)}},$0≦m≦N_(ZC) ^(RS)−1 with q given by q=└q+½┘+v·(−1)^(└2q┘) and q given byq=N_(ZC) ^(RS)·(u+1)/31. The length N_(ZC) ^(RS) of a ZC sequence isgiven by the largest prime number such that N_(ZC) ^(RS)<M_(sc) ^(RS).Multiple RS sequences are defined from a single base sequence throughdifferent values of α. A PUCCH transmission is assumed to be in one RB(M_(sc) ^(RS)=N_(sc) ^(RB)).

FIG. 4 is a diagram illustrating a conventional transmitter for a ZCsequence.

Referring to FIG. 4, a mapper 420 maps a ZC sequence 410 to REs of anassigned transmission BW as they are indicated by RE selection unit 425.Subsequently, an IFFT is performed by IFFT unit 430, a CS is applied tothe output by CS unit 440, followed by scrambling with a cell-specificsequence using scrambler 450, a Cyclic Prefix (CP) is inserted by CPinsertion unit 460, and the resulting signal is filtered by filter 470.Finally, a transmission power P_(PUCCH) is applied by power amplifier480 and the ZC sequence is transmitted 490.

Different CSs of a ZC sequence provide orthogonal ZC sequences.Therefore, different CSs of a same ZC sequence are allocated todifferent UEs in a same PUCCH RB and achieve orthogonal multiplexing forrespective HARQ-ACK signal and RS transmissions. Orthogonal multiplexingcan also be in the time domain using Orthogonal Covering Codes (OCCs)where PUCCH symbols used for HARQ-ACK signal or RS transmission in eachslot are respectively multiplied with a first OCC and a second OCC. Forexample, for the structure in FIG. 3, HARQ-ACK signal transmission ismodulated by a length-4 OCC, such as a Walsh-Hadamard (WH) OCC, while RStransmission is modulated by a length-3 OCC, such as a Discrete FourierTransform (DFT) OCC. In this manner, the multiplexing capacity isincreased by a factor of 3 (determined by the OCC with the smallerlength N_(oc)). The WH OCCs, {W₀, W₁, W₂, W₃}, and DFT OCCs, {D₀, D₁,D₂}, are:

${\begin{bmatrix}W_{0} \\W_{1} \\W_{2} \\W_{3}\end{bmatrix} = \begin{bmatrix}1 & 1 & 1 & 1 \\1 & {- 1} & 1 & {- 1} \\1 & 1 & {- 1} & {- 1} \\1 & {- 1} & {- 1} & 1\end{bmatrix}},{\begin{bmatrix}D_{0} \\D_{1} \\D_{2}\end{bmatrix} = {\begin{bmatrix}1 & 1 & 1 \\1 & e^{{- j}\; 2\;{\pi/3}} & e^{{- j}\; 4\;{\pi/3}} \\1 & e^{{- j}\; 4\;{\pi/3}} & e^{{- j}\; 2\;{\pi/3}}\end{bmatrix}.}}$

Table 1 presents a mapping of a PUCCH resource n_(PUCCH) to an OC n_(oc)and a CS α for a HARQ-ACK signal and RS transmission. For brevity, theRS associated with the HARQ-ACK signal will not be mentioned in thefollowing. As a PUCCH is assumed to be transmitted over 1 RB including12 REs, there is a total of 12 CS for a ZC sequence.

TABLE 1 HARQ-ACK Signal and RS Resource Mapping to OC and CS OC n_(oc)for HARQ-ACK Signal and for RS CS α W₀, D₀ W₁, D₁ W₃, D₂ 0 n_(PUCCH) = 0n_(PUCCH) = 12 1 n_(PUCCH) = 6 2 n_(PUCCH) = 1 n_(PUCCH) = 13 3n_(PUCCH) = 7 4 n_(PUCCH) = 2 n_(PUCCH) = 14 5 n_(PUCCH) = 8 6 n_(PUCCH)= 3 n_(PUCCH) = 15 7 n_(PUCCH) = 9 8 n_(PUCCH) = 4 n_(PUCCH) = 16 9n_(PUCCH) = 10 10 n_(PUCCH) = 5 n_(PUCCH) = 17 11 n_(PUCCH) = 11

A UE can determine a conventional PUCCH resource n_(PUCCH) for itsHARQ-ACK signal transmission either through explicit signaling fromserving TP(s) or through implicit signaling. The latter is based on CCEsused to transmit a PDCCH conveying a respective DL SA in response towhich a UE transmits a HARQ-ACK signal. A one-to-one mapping may existbetween conventional PUCCH resources used to transmit HARQ-ACK signalsand CCEs used to transmit PDCCHs. For example, for UEs with onetransmitter antenna port and a PDCCH transmission structure as in FIG.2, a UE determines a conventional PUCCH resource for HARQ-ACK signalingfrom a CCE with a lowest index from a respective DL SA transmission.Then, UE1, UE2, UE3, and UE4 can respectively use PUCCH resource 1, 5,7, and 9. If all PUCCH resources within an RB are used, resources in theimmediately next RB are used. In general, a UE can determine aconventional PUCCH resource n_(PUCCH) for HARQ-ACK signaling asn_(PUCCH)=n_(CCE)+N_(PUCCH) where n_(CCE) is a CCE with a lowest indexfor a respective DL SA and N_(PUCCH) is TP-specific offset that isinformed to UEs by higher layer signaling.

Improving coverage and cell-edge throughput are key objectives incommunication systems. Coordinated Multi-Point transmission/reception(CoMP) is an important technique to achieve these objectives. CoMPoperation relies on the fact that when a UE is in a cell-edge region, itis able to reliably receive a signal combined at a set of TPs (DL CoMP)and reliably transmit a signal combined at a set of RPs (UL CoMP). DLCoMP schemes can range from simple ones of interference avoidance, suchas coordinated scheduling, to more complex ones requiring accurate anddetailed channel information such as joint transmission from multipleTPs. UL CoMP schemes can also range from simple ones where PUSCHscheduling is performed considering a single RP to more complex oneswhere received signal characteristics and generated interference atmultiple RPs are considered.

FIG. 5 is a diagram illustrating a conventional UL CoMP operation.

Referring to FIG. 5, a signal transmitted by a UE 510 is received fromtwo RPs, RP1 520 and RP2 530. Scheduling coordination between the twoRPs and combining of the respective received signals is facilitated by afast backhaul link such as an optical fiber link.

Support of UL CoMP introduces new requirements for HARQ-ACK signaling ina PUCCH. As conventional HARQ-ACK signaling scrambles a respective ZCsequence with a respective RP-specific (cell-specific) sequence, it isnot possible to support orthogonal multiplexing of HARQ-ACK signals in asame RB for reception at multiple RPs. For this reason, separate PUCCHRBs should be used for UL CoMP reception of HARQ-ACK signals. Thescrambling of such HARQ-ACK signals is with a scrambling sequence thatis common for all RPs constituting a set of UL CoMP RPs for a respectiveset of UEs (a CoMP-set specific ZC sequence is UE-specific and signaledto a UE by higher layer signaling).

The need to provide non-conventional PUCCH resources to supportorthogonal multiplexing of HARQ-ACK signals for reception at multipleRPs, relative to conventional PUCCH resources supporting orthogonalmultiplexing of HARQ-ACK signals for reception at a single RP, isassociated with a respective increase in the UL overhead which reducesUL throughout.

Additionally, if both a conventional PDCCH and non-conventional PDCCHtypes are transmitted in a same subframe, collisions of PUCCH resourcesmay occur, if the respective CCEs of the various PDCCH types areindependently indexed and non-conventional PUCCH resources may then needto be configured for each of the non-conventional PDCCH types.

Therefore, there is a need to reduce an overhead resulting fromassigning non-conventional PUCCH resources for transmissions of HARQ-ACKsignals.

There is another need to provide mappings for compressing an amount ofnon-conventional PUCCH resources for HARQ-ACK signaling.

Finally, there is another need for indicating to a UE whether to use aconventional PUCCH resource or a non-conventional PUCCH resource for itsHARQ-ACK signaling.

SUMMARY OF THE INVENTION

Accordingly, an aspect of the present invention is to solve at least theabove-described problems occurring in the prior art and at least theadvantages described below.

Another aspect of the present invention is to provide methods andapparatus for performing HARQ-ACK signal transmissions while providingcompression of respective resources and providing mechanisms forselecting between conventional PUCCH resources and non-conventionalPUCCH resources.

According to an aspect of the present invention, a method is providedfor a UE to transmit an acknowledgement/negative acknowledgement(ack/nack) signal. The method includes receiving configurationinformation through higher layer signaling; determining a first resourceor a second resource based on the received configuration information;transmitting the ack/nack signal using a first sequence on the firstresource, if the first resource is determined; and transmitting theack/nack signal using a second sequence on the second resource, if thesecond resource is determined.

According to another aspect of the present invention, a method isprovided for a base station to receive an ack/nack signal. The methodincludes transmitting configuration information through higher layersignaling; determining a first resource or a second resource based onthe transmitted configuration information; receiving the ack/nack signalusing a first sequence on the first resource, if the first resource isdetermined; and receiving the ack/nack signal using a second sequence onthe second resource, if the second resource is determined.

According to another aspect of the present invention, a UE configured totransmit an ack/nack signal is provided. The UE includes a receiverconfigured to receive configuration information through higher layersignaling; a controller configured to determine a first resource or asecond resource based on the received configuration information; and atransmitter configured to transmit the ack/nack signal using a firstsequence on the first resource, if the first resource is determined, andto transmit the ack/nack signal using a second sequence on the secondresource, if the second resource is determined.

According to another aspect of the present invention, a base stationconfigured to receive an ack/nack signal is provided. The base stationincludes a transmitter configured to transmit configuration informationthrough higher layer signaling; a controller configured to determine afirst resource or a second resource based on the transmittedconfiguration information; and a receiver configured to receive theack/nack signal using a first sequence on the first resource, if thefirst resource is determined, and to receive the ack/nack signal using asecond sequence on the second resource, if the second resource isdetermined.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating a conventional structure for a DLcontrol region in a DL TTI;

FIG. 2 is a diagram illustrating a conventional PDCCH transmissionprocess;

FIG. 3 is a diagram illustrating a conventional structure for HARQ-ACKsignal transmission in a PUCCH;

FIG. 4 is a block diagram illustrating a conventional transmitter for aZC sequence;

FIG. 5 is a diagram illustrating a conventional UL CoMP operation;

FIG. 6 is a diagram illustrating a mapping of PDCCH CCEs tonon-conventional PUCCH resources used for HARQ-ACK signaling from UEs byexcluding CSS CCEs, according to an embodiment of the present invention;

FIG. 7 is a diagram illustrating a mapping of PDCCH CCEs to PUCCHresources for HARQ-ACK signaling from UEs by compressing a mapping ofN_(COMP) CCEs to a single PUCCH resource, according to an embodiment ofthe present invention;

FIG. 8 is a diagram illustrating a process for a UE to determine a firstnon-conventional PUCCH resource for a HARQ-ACK signaling, according toan embodiment of the present invention;

FIG. 9 is a diagram illustrating a placement of RBs for various types ofUL resources in a UL BandWidth (BW), according to an embodiment of thepresent invention;

FIG. 10 is a diagram illustrating a process for a UE to determine aPUCCH resource for its HARQ-ACK signaling using a “PUCCH ResourceIndication” field in a DL SA, according to an embodiment of the presentinvention; and

FIG. 11 is a diagram illustrating a process for a UE to determine aPUCCH resource for its HARQ-ACK signaling according to a subframepattern signaled by higher layers, according to an embodiment of thepresent invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

Various embodiments of the present invention will now be described indetail with reference to the accompanying drawings. This presentinvention may, however, be embodied in many different forms and shouldnot be construed as limited to the embodiments described herein.

Additionally, although the embodiments of the present invention aredescribed below with reference to Discrete Fourier Transform(DFT)-spread Orthogonal Frequency Division Multiplexing (OFDM), theyalso are applicable to all Frequency Division Multiplexing (FDM)transmissions in general and to OFDM in particular.

Moreover, although the embodiments of the present invention for HARQ-ACKsignaling in non-conventional PUCCH resources will be described belowwith respect to a UL CoMP operation, they are also applicable to anysuch HARQ-ACK signaling in general and to HARQ-ACK signaling in responseto a detected non-conventional PDCCH type in particular.

According to one aspect of the present invention, there are provideddesigns for implicit mappings compressing an amount of non-conventionalPUCCH resources required to support transmissions of HARQ-ACK signalsfrom UEs. These non-conventional PUCCH resources are in different RBsthan PUCCH resources used for conventional HARQ-ACK signaltransmissions. A UE is configured by higher layer signaling to useeither conventional PUCCH resources or non-conventional PUCCH resourcesfor its HARQ-ACK signal transmission. In the former case, a UE uses aTP-specific ZC sequence for HARQ-ACK signaling while in the latter casea UE uses a UE-specific ZC sequence for HARQ-ACK signaling that isinformed to the UE by higher layer signaling. Dynamic selection betweenconventional and non-conventional PUCCH resources is also addressedbelow.

Table 2 lists a number of PUCCH RBs required for HARQ-ACK signalingusing a conventional, one-to-one, mapping between a PDCCH CCE and aPUCCH resource. It is assumed that a DL system BW includes N_(RB)^(max,DL)=100 RBs (each RB includes N_(sc) ^(RB)=12 REs) and a RStransmission in a DL control region is from two antenna ports and onlyin a first OFDM symbol, as illustrated in FIG. 1. Furthermore, it isassumed that there are 4 REGs for PCFICH transmission and 6 REGs forPHICH transmissions. If a fractional PUCCH RB is needed for HARQ-ACKsignal transmission, it is assumed to be rounded to a whole RB if it maynot support transmission of signals other than HARQ-ACK signals. Then,for N_(CCE) CCEs available for PDCCH transmissions (a DL subframe indexis omitted for simplicity), a number of PUCCH RBs for HARQ-ACK signaltransmissions is ┌N_(CCE)·Δ_(shift) ^(PUCCH)/(N_(sc) ^(RB)·N_(oc))┐where ┌ ┐ is the “ceiling” function which rounds a number to itsimmediately larger integer.

TABLE 2 Number of CCEs for PDCCHs and Number of PUCCH RBs for HARQ-ACKSignals Number of OFDM symbols in a DL control region 3 2 Number of CCEsfor PDCCHs 87 54 Number of PUCCH RBs for HARQ-ACK Signals, Δ_(shift)^(PUCCH) = 3 ┌87 · 3/(12 · 3)┐ = 8 ┌54 · 3/(12 · 3)┐ = 5 Number of PUCCHRBs for HARQ-ACK Signals, Δ_(shift) ^(PUCCH) = 2 ┌87 · 2/(12 · 3)┐ = 5┌54 · 2/(12 · 3)┐ = 3

As evident in Table 2, for a given number of TP antenna ports and agiven number of PCFICH and PHICH REGs, PUCCH overhead for HARQ-ACKsignaling is variable, depends on a number of OFDM symbols of a DLcontrol region and on a value of Δ_(shift) ^(PUCCH), and can reach amaximum value of 8 RBs.

If the conventional derivation of PUCCH resources is also applied forderiving non-conventional PUCCH resources for HARQ-ACK signaling then,for a UL system BW including N_(RB) ^(max,UL)=100 RBs, thenon-conventional resource overhead can reach 8% and this directlydecreases UL throughput by at least a same amount. A significant ULthroughput reduction occurs even for the smaller non-conventionalresource overhead values.

A reduction in UL overhead due to the non-conventional PUCCH resourcescan be achieved by using different mappings between the PDCCH CCEs andthe non-conventional PUCCH resources for transmissions of HARQ-ACKsignals in order to achieve compression for the latter. As in theexample in Table 2 the total number of PDCCH CCEs can be 87 while thetotal number of PDCCHs conveying DL SAs in a subframe is typically lessthan 10, substantial redundancy exists in the one-to-one mapping betweenPDCCH CCEs and PUCCH resources for transmissions of HARQ-ACK signals.

A first approach to compress non-conventional PUCCH resources forHARQ-ACK signaling is to exclude from the mapping the N_(CCE) ^(CCS)CCEs of the CSS as respective PDCCH transmissions typically addressgroups of UEs and respective HARQ-ACK signaling may not exist. Even ifsome CCEs of the CSS are used to transmit SAs, these SAs can be limitedto UL SAs or to SAs for UEs for which transmissions of HARQ-ACK signalsare not intended to be orthogonally multiplexed for reception at a sameset of multiple RPs. Then, N_(CCE)−N_(CCE) ^(CSS) non-conventional PUCCHresources corresponding to ┌(N_(CCE)−N_(CCE) ^(CSS))·Δ_(shift)^(PUCCH)/(N_(sc) ^(RB)·N_(oc))┐ RBs are allocated for HARQ-ACKsignaling.

Table 3 lists a corresponding number of PUCCH RBs for HARQ-ACK signalingexcluding N_(CCE) ^(UE-CSS)=16 CCEs of the CSS.

TABLE 3 PUCCH RBs for HARQ-ACK signals excluding CSS CCEs from resourcemapping. Number of OFDM symbols in a DL control region 3 2 Number ofCCEs for PDCCHs 71 38 Number of PUCCH RBs for HARQ-ACK Signals,Δ_(shift) ^(PUCCH) = 3 ┌71 · 3/(12 · 3)┐ = 6 ┌38 · 3/(12 · 3)┐ = 4Number of PUCCH RBs for HARQ-ACK Signals, Δ_(shift) ^(PUCCH) = 2 ┌71 ·2/(12 · 3)┐ = 4 ┌38 · 2/(12 · 3)┐ = 3

As evident in Table 3, a maximum number of non-conventional PUCCH RBs isreduced by 2 representing a 25% reduction. Further, by applying a minorscheduling restriction and not using the last 2 CCEs to convey DL SAs toUEs for which HARQ-ACK signals are to be orthogonally received at a sameset of multiple RPs, a number of RBs required for HARQ-ACK signalingwhen a DL control region includes 2 OFDM symbols is 3 for Δ_(shift)^(PUCCH)=3 and 2 for Δ_(shift) ^(PUCCH)=2 (and not 4 and 3 as listed inTable 2). Therefore, a total UL overhead reduction of 2% is achieved byexcluding CSS CCEs from mapping to non-conventional PUCCH resources forHARQ-ACK signaling.

FIG. 6 is a diagram illustrating a mapping of PDCCH CCEs tonon-conventional PUCCH resources for HARQ-ACK signaling from UEs byexcluding CSS CCEs.

Referring to FIG. 6, a UE determines a number N_(CCE) of CCEs availablefor PDCCH transmissions from a value conveyed in a PCFICH 610. If a UEincorrectly decodes a PCFICH then, due to interleaving of PDCCH CCEs, itwill also miss its DL SA (if any) and will therefore not transmit aHARQ-ACK signal. From the N_(CCE) CCEs, a UE excludes the N_(CCE) ^(CSS)CSS CCEs (which are predetermined in the system operation) and considersonly the remaining N_(CCE)−N_(CCE) ^(CSS) CCEs for determiningnon-conventional PUCCH resources for HARQ-ACK signaling 620. Finally,using a one-to-one mapping between remaining CCEs and non-conventionalPUCCH resources for HARQ-ACK signaling, a UE determines N_(CCE)−N_(CCE)^(CSS) such non-conventional PUCCH resources corresponding to┌(N_(CCE)−N_(CCE) ^(CSS))·Δ_(shift) ^(PUCCH)/(N_(sc) ^(RB)·N_(oc))┐ RBs630.

A second approach to reduce an overhead for non-conventional PUCCHresources for HARQ-ACK signaling from UEs is to increase a granularityof CCE mapping to a PUCCH resource. Instead of a conventional mappinguniquely linking one CCE with one PUCCH resource, N_(COMP) consecutiveCCEs in the logical domain (prior to interleaving) can be linked with asingle non-conventional PUCCH resource for HARQ-ACK signaling. Then,non-conventional PUCCH resources can be compressed by a factor ofN_(COMP).

Table 4 lists a number of PUCCH RBs for HARQ-ACK signaling when a PUCCHresource corresponds to N_(COMP)=2 CCEs.

TABLE 4 PUCCH RBs for HARQ-ACK Signaling - Mapping of 2 CCEs to onePUCCH Resource Number of OFDM symbols in a DL control region 3 2 Numberof CCEs for PDCCHs 87 54 Number of PUCCH RBs for HARQ-ACK Signals,Δ_(shift) ^(PUCCH) = 3 ┌87 · 3/(12 · 3 · 2)┐ = 4 ┌54 · 3/(12 · 3 · 2)┐ =3 Number of PUCCH RBs for HARQ-ACK Signals, Δ_(shift) ^(PUCCH) = 2 ┌87 ·2/(12 · 3 · 2)┐ = 3 ┌54 · 2/(12 · 3 · 2)┐ = 2

As evident in Table 4, a maximum number of non-conventional PUCCH RBs isreduced by 4 representing a total UL overhead reduction of 4% and areduction of 50% in a number of non-conventional PUCCH RBs.

FIG. 7 is a diagram illustrating a mapping of PDCCH CCEs to PUCCHresources for HARQ-ACK signaling from UEs by compressing a mapping ofN_(COMP) CCEs to a single PUCCH resource.

Referring to FIG. 7, a UE determines a number N_(CCE) of CCEs availablefor PDCCH transmissions from a value conveyed in a PCFICH 710. From anumber of N_(CCE) CCEs, a UE determines ┌N_(CCE)/N_(COMP)┐ groups ofN_(COMP) elements (the last group hasN_(CCE)−└N_(CCE)/N_(COMP)┘·N_(COMP) elements) 720. Finally, from anumber of ┌N_(CCE)/N_(COMP)┐ groups and using a one-to-one mapping, a UEdetermines ┌N_(CCE)/N_(COMP)┐ PUCCH resources 730 available for HARQ-ACKsignaling corresponding to ┌┌N_(CCE)/N_(COMP)┐·Δ_(shift)^(PUCCH)/(N_(sc) ^(RB)·N_(oc))┐ RBs and uses a resource determined frommapping a lowest CCE index in a respective DL SA to a group.

The first approach and the second approach can be combined to offerincreased compression in a number of non-conventional PUCCH resourcesfor HARQ-ACK signaling from UEs. Table 5 lists a corresponding number ofPUCCH RBs for HARQ-ACK signaling when the previous first and secondapproaches are combined.

TABLE 5 Number of PUCCH RBs for HARQ-ACK signaling excluding CSS CCEsfrom PUCCH resource mapping and mapping N_(COMP) = 2 CCEs to a singlePUCCH resource. Number of OFDM symbols in a DL control region 3 2 Numberof CCEs for PDCCHs 71 38 Number of PUCCH RBs for HARQ-ACK Signals,Δ_(shift) ^(PUCCH) = 3 ┌71 · 3/(12 · 3 · 2)┐ = 3 ┌38 · 3/(12 · 3 · 2)┐ =2 Number of PUCCH RBs for HARQ-ACK Signals, Δ_(shift) ^(PUCCH) = 2 ┌71 ·2/(12 · 3 · 2)┐ = 2 ┌38 · 2/(12 · 3 · 2)┐ = 2

As evident in Table 5, a maximum number of non-conventional PUCCH RBs isreduced by 5 representing a total UL overhead reduction of 5% and areduction of 62.5% in a number of non-conventional PUCCH RBs. Therefore,a maximum non-conventional UL overhead to support orthogonal receptionof HARQ-ACK signals is 3% and can often be reduced to 2% or even 1% (fora DL control region of 2 OFDM symbols and for Δ_(shift) ^(PUCCH)=2 whenthe last 2 CCEs in the logical domain are not used to transmit DL SAs toUEs configured use of non-conventional PUCCH resources for HARQ-ACKsignaling).

A UE configured for HARQ-ACK signaling in non-conventional PUCCHresources can determine a starting resource either from a PCFICH if allthese UEs are served by a same TP or from higher layer signaling if atleast some of these UEs are served by different or multiple TPs. In theformer approach, based on a PCFICH detection indicating a size of a DLcontrol region conveying DL SAs, a UE can determine a number of PDCCHCCEs and can therefore determine a last conventional PUCCH resource forHARQ-ACK signaling. The non-conventional PUCCH resources for HARQ-ACKsignaling may then start at the next RB or the next resource. In thelatter approach, a UE is explicitly configured a first non-conventionalPUCCH resource for HARQ-ACK signaling.

FIG. 8 is a diagram illustrating a process for a UE to determine a firstnon-conventional PUCCH resource for a HARQ-ACK signaling.

Referring to FIG. 8, a UE configured for HARQ-ACK signaling innon-conventional PUCCH RBs, in addition to receiving a first higherlayer signaling indicating a N_(PUCCH) value for a resource in a firstconventional PUCCH RB for HARQ-ACK signaling, it also receives a secondhigher layer signaling indicating a value for determining a firstnon-conventional resource in a PUCCH RB for HARQ-ACK signaling 810. TheUE then examines whether it is configured to use a PCFICH to determine afirst non-conventional PUCCH RB for HARQ-ACK signaling 820. If it is, aUE determines a first non-conventional PUCCH RB for HARQ-ACK signalingbased on a value provided by a PCFICH 830 by determining a number ofCCEs available for PDCCH transmissions and then determining respectivePUCCH RBs for conventional HARQ-ACK signaling. A first non-conventionalPUCCH RB for HARQ-ACK signaling is the first one after a conventionalPUCCH RBs for HARQ-ACK signaling. If it is not, a UE determines a firstnon-conventional PUCCH RB being the one indicated by the second higherlayer signaling 840.

A UE using a non-conventional PUCCH resource for HARQ-ACK signalingdetermines such resource n_(PUCCH) ^(COMP) as n_(PUCCH)^(COMP)=f(n_(CCE))+N_(PUCCH) ^(COMP) where f(n_(CCE)) is a function ofthe PDCCH CCE(s) used to convey a DL SA in response to which a UEtransmits a HARQ-ACK signal and N_(PUCCH) ^(COMP) is an offset informedto a UE by higher layer signaling.

For the first of the previously described approaches (CCEs of CSS areexcluded from determining non-conventional PUCCH resources for HARQ-ACKsignaling), f(n_(CCE))=n_(CCE)−N_(CCE) ^(CSS). For the second of thepreviously described approaches (CCEs of CSS are not excluded fromdetermining non-conventional PUCCH resources for HARQ-ACK signaling),f(n_(CCE))=┌n_(CCE)/N_(COMP)┐. For the combination of the first andsecond approaches, f(n_(CCE))=┌(n_(CCE)−N_(CCE) ^(CSS))/N_(COMP)┐. Ifthe conventional approach is used, f(n_(CCE))=n_(CCE).

If a UE determines a first non-conventional resource for HARQ-ACKsignaling from a PCFICH, then N_(PUCCH)^(COMP)=┌(N_(CCE)+N_(PUCCH))·Δ_(shift) ^(PUCCH)/(N_(sc) ^(RB)·N_(oc))┐;otherwise, N_(PUCCH) ^(COMP) is the value configured by theaforementioned second higher layer signaling.

FIG. 9 is a diagram illustrating a placement of RBs for various types ofUL resources in a UL BW.

Referring to FIG. 9, a UL BW includes RBs for conventional PUCCHresources for HARQ-ACK signaling 920 and 925, RBs for non-conventionalPUCCH resources for HARQ-ACK signaling 930 and 935, RBs for PUCCHresources for other UCI signaling (may also include other HARQ-ACKsignaling) 910 and 915, and PUSCH RBs for data/UCI signaling 940.

According to an aspect of the present invention, there is provided adesign to dynamically indicate to a UE whether to use conventional PUCCHresources or non-conventional PUCCH resources for its HARQ-ACKsignaling.

The need to indicate to a UE whether to use conventional PUCCH resourcesor non-conventional PUCCH resources for its HARQ-ACK signaling ismotivated by an objective to minimize a non-conventional UL overheadassociated with the latter resources. For example, when the number ofUEs benefiting from orthogonal reception of their HARQ-ACK signals at asame set of multiple RPs in a subframe is small, respectivenon-conventional PUCCH resources are not used and instead assigned toPUSCHs. The reverse applies when a number of such UEs is large.Additionally, a UE may detect conventional PDCCH in some subframes anduse a conventional PUCCH resource for a respective HARQ-ACK signaltransmission while it detects a non-conventional PDCCH in othersubframes and use a non-conventional PUCCH resource for a respectiveHARQ-ACK signal transmission. In general, there is a need to enable anetwork with the choice to assign non-conventional PUCCH resources toHARQ-ACK signaling depending on scheduling decisions in a respectivesubframe.

A first approach is to dynamically indicate to a UE whether to use aconventional PUCCH resource or a non-conventional PUCCH resource for itsHARQ-ACK signaling by including a respective “PUCCH Resource Indication”field of 1 bit in a respective DL SA.

Depending on a value of a “PUCCH Resource Indication” field, a UE maytransmit its HARQ-ACK signal using a conventional PUCCH resource, forexample when the field has a binary 0 value, or using a non-conventionalPUCCH resource, for example when the field has a binary 1 value.

FIG. 10 is a diagram illustrating a process for a UE to determine aPUCCH resource for its HARQ-ACK signaling using a “PUCCH ResourceIndication” field in a DL SA.

Referring to FIG. 10, a DL SA includes a field including 1 bit 1010 andindicating whether a respective HARQ-ACK signal transmission should usea conventional or a non-conventional PUCCH resource. Based on a value ofthis field 1020, a UE transmits its HARQ-ACK signal in a conventionalPUCCH resource for example when a value of the field is a binary ‘0’1030, or in a non-conventional PUCCH resource for example when a valueof the field is a binary ‘1’ 1040.

A second approach is to link a PUCCH resource used by a UE for itsHARQ-ACK signaling to a subframe a UE receives a respective DL SA. A UEis informed of this link by higher layer signaling of a subframepattern. For example, for a frame duration of 10 subframes, a UE can beconfigured a pattern (bit-map) applicable in every frame and including10 values of binary zeros or binary ones with a binary zero indicatingthat a UE should use a conventional PUCCH resource and a binary oneindicating that a UE should use an non-conventional PUCCH resource forits HARQ-ACK signaling. A use of a conventional PUCCH resource isassociated with a respective detected conventional PDCCH type and a useof a non-conventional PUCCH resource is associated with a respectivedetected non-conventional PDCCH type.

Compared to the first approach, the second approach does not change asize of a DL SA but restricts the flexibility of HARQ-ACK signaling tobenefit from orthogonal reception at a same set of multiple RPs. Basedon a tradeoff between non-conventional PUCCH overhead versus improvedHARQ-ACK reception reliability, a scheduler can determine whether totransmit a DL SA to a UE in a subframe associated with non-conventionalPUCCH resources or in a subframe associated with conventional PUCCHresources for HARQ-ACK signaling. For example, a scheduler may decide topositively bias a decision for transmission of DL SAs to respective UEsin former subframes and negatively bias such a decision in lattersubframes.

FIG. 11 is a diagram illustrating a process for a UE to determine aPUCCH resource for its HARQ-ACK signaling according to a subframepattern signaled by higher layers.

Referring to FIG. 11, a UE is signaled by higher layers a subframepattern for a determination of a conventional or a non-conventionalPUCCH resource for its HARQ-ACK signaling 1110. For example, for a frameincluding 10 subframes a pattern (bit-map) that is applicable to everyframe is {1 0 0 1 1 1 0 0 0 1} where a binary ‘0’ indicates use of aconventional PUCCH resource (and a binary ‘1’ indicates use of anon-conventional PUCCH resource. A UE examines whether a subframe of itsDL SA reception is associated with a use of a conventional PUCCHresource or a use of a non-conventional PUCCH resource 1120 for arespective HARQ-ACK signal transmission. If the subframe pattern has avalue of binary ‘0’ for a subframe a UE receives a DL SA, a UE uses aconventional PUCCH resource for respective HARQ-ACK signaling 1130. Ifthe subframe pattern has a value of binary ‘1’ for a subframe a UEreceives a DL SA, a UE uses a non-conventional PUCCH resource forrespective HARQ-ACK signaling 1140. Further, although not illustrated inthe drawings, a UE may also include a selector, a mapper, a transmitter,and a receiver. The selector selects a first resource in firstresources, if the first sequence is used, wherein the first resource isdetermined from a sum of a lowest CCE index of the control channel and afirst offset, and wherein the first resource is located between thirdresources used for transmissions of periodic control signals using oneof the first sequence or the second sequence and second resources usedfor transmissions of dynamic control signals using the second sequence,or selects a second resource in second resources, if the second sequenceis used, wherein the second resource is determined from a sum of thelowest CCE index of the control channel and a second offset, and whereinthe third resources are located near each end of an operating bandwidth.The transmitter transmits the control signal in the first resource or inthe second resource.

The mapper maps a sum of a lowest CCE index of the detected controlchannel and a first offset to a first resource, or maps a sum of alowest index of a group of CCEs with consecutive indexes, containing aCCE with a lowest index of the detected control channel, and the secondoffset to a second resource. The transmitter configured to transmit thecontrol signal in the first resource or in the second resource.

The receiver receives signaling of a bit-map with a size equal to anumber of subframes in a frame. The mapper maps a bit in the bit-map tothe subframe of the control channel detection. The transmitterconfigured to transmit the control signal in a first resource, if thebit has a first binary value or in a second resource, if the bit has asecond binary value.

While the present invention has been shown and described with referenceto certain embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the spirit and scope of the present invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method for a user equipment (UE) to transmit anacknowledgement/negative acknowledgement (ack/nack) signal, the methodcomprising: receiving configuration information through higher layersignaling; receiving at least one data transport block; determining afirst resource or a second resource based on the received configurationinformation; transmitting an ack/nack signal associated with thereceived at least one data transport block using a first sequence on thefirst resource, if the configuration information informs about the firstsequence, wherein the first resource is determined based on a lowestcontrol channel element (CCE) index of a control channel and a firstoffset configured by the configuration information; and transmitting theack/nack signal associated with the received at least one data transportblock using a second sequence on the second resource, if theconfiguration information does not inform about the first sequence,wherein the second resource is determined based on the lowest CCE indexof the control channel and a second offset configured by theconfiguration information, wherein the first offset is UE-specific. 2.The method of claim 1, wherein the first sequence and the secondsequence are generated based on a Zadoff-Chu sequence.
 3. A method for abase station to receive an acknowledgement/negative acknowledgement(ack/nack) signal, the method comprising: transmitting configurationinformation through higher layer signaling; transmitting at least onedata transport block; determining a first resource or a second resourcebased on the transmitted configuration information; receiving anack/nack signal associated with the transmitted at least one datatransport block using a first sequence on the first resource, if theconfiguration information informs about the first sequence, wherein thefirst resource is determined based on a lowest control channel element(CCE) index of a control channel and a first offset configured by theconfiguration information; and receiving the ack/nack signal associatedwith the transmitted at least one data transport block using a secondsequence on the second resource, if the configuration information doesnot inform about the first sequence, wherein the second resource isdetermined based on the lowest CCE index of the control channel and asecond offset configured by the configuration information, wherein thefirst offset is user equipment (UE)-specific.
 4. The method of claim 3,wherein the first sequence and the second sequence are generated basedon a Zadoff-Chu sequence.
 5. A user equipment (UE) configured totransmit an acknowledgement/negative acknowledgement (ack/nack) signal,the UE comprising: a receiver configured to: receive configurationinformation through higher layer signaling, and receive at least onedata transport block; a controller configured to determine a firstresource or a second resource based on the received configurationinformation; and a transmitter configured to: transmit an ack/nacksignal associated with the received at least one data transport blockusing a first sequence on the first resource, if the configurationinformation informs about the first sequence, wherein the first resourceis determined based on a lowest control channel element (CCE) index of acontrol channel and a first offset configured by the configurationinformation, and transmit the ack/nack signal associated with thereceived at least one data transport block using a second sequence onthe second resource, if the configuration information does not informabout the first sequence, wherein the second resource is determinedbased on the lowest CCE index of the control channel and a second offsetconfigured by the configuration information, wherein the first offset isUE-specific.
 6. The UE of claim 5, wherein the first sequence and thesecond sequence are generated based on a Zadoff-Chu sequence.
 7. A basestation configured to receive an acknowledgement/negativeacknowledgement (ack/nack) signal, the base station comprising: atransmitter configured to: transmit configuration information throughhigher layer signaling, and transmit at least one data transport block;a controller configured to determine a first resource or a secondresource based on the transmitted configuration information; and areceiver configured to: receive an ack/nack signal associated with thetransmitted at least one data transport block using a first sequence onthe first resource, if the configuration information informs about thefirst sequence, wherein the first resource is determined based on alowest control channel element (CCE) index of a control channel and afirst offset configured by the configuration information, and receivethe ack/nack signal associated with the transmitted at least one datatransport block using a second sequence on the second resource, if theconfiguration information does not inform about the first sequence,wherein the second resource is determined based on the lowest CCE indexof the control channel and a second offset configured by theconfiguration information, wherein the first offset is user equipment(UE)-specific.
 8. The base station of claim 7, wherein the firstsequence and the second sequence are generated based on a Zadoff-Chusequence.